Gripping jaws for cold heading machine

ABSTRACT

Gripping jaws in a machine for cold heading high tensile strength steel wire that is greasy, in which the gripping jaws have a plurality of projecting wire gripping portions arranged to engage the wire at spaced intervals along its length and are grooved to receive the wire, the one gripping jaw being stationary and the other being movable toward the stationary one by means of a hydraulic cylinder. The projecting gripping portions project so that longer and shorter gripping portions alternate along the length of the wire and the longer gripping portions on the one jaw are opposite the shorter gripping portions of the other jaw so as to slightly deflect the wire gripped by the jaws first in one direction and then in the opposite direction so as to cause a waviness or undulation in the wire when it is gripped, which is so slight that the wire is not permanently deformed. This prevents any slippage of the wire when the heading die is forming a button head on the wire, the heading movement of the die being endwise of the wire toward the gripping jaws. To grip a wire, approximately one-quarter inch in diameter, the variation in the projection of the gripping portions of the jaws is preferably only 0.005 inch.

United States Patent [451 May 30, 1972 211 App]. No.: 34,304

521 05.0 ..72/304,269/265,269/269 511 Int. C l ...B2 ldll/Q} s FleldoiSearch ..72/304,308,309,DIG.16;

Primary Examiner-Charles W. Lanham Assistant ExaminerMichael J. Keenan Attorney-Alfred R. Fuchs [57] ABSTRACT Gripping jaws in a machine for cold heading high tensile strength steel wire that is greasy, in which the gripping jaws have a plurality of projecting wire gripping portions arranged to engage the wire at spaced intervals along its length and are grooved to receive the wire, the one gripping jaw being stationary and the other being movable toward the stationary one by means of a hydraulic cylinder. The projecting gripping portions project so that longer and shorter gripping portions alternate along the length of the wire and the longer gripping portions on the one jaw are opposite the shorter gripping portions of the other jaw so as to slightly deflect the wire gripped by the jaws first in one direction and then in the opposite direction so as to cause a waviness or undulation in the wire when it is gripped, which is so slight that the wire is not permanently deformed. This prevents any slippage of the wire [56] References Cited when the heading die is forming a button head on the wire, the- UNITED STATES PATENTS heading movement of the die being endwise of the wire toward the gnppmg jaws. To grip a wire, approximately one-quarter 3,333,456 8/1967 Dab ney et al ..72/453 h i diameter, the variation in the projection f the gripping 1,025,739 5/1912 Davis .269/272 portions fth j is f bl only 0005 inch. 3,299,689 l/l967 Dolney et al ..72/304 2,485,354 l 949 Brennan ..72/ 304 3 Claims, 5 Drawing Figures 22 E I l kal 2o 22 2| 5 fizz:

23 3o 29 33 29 3 28 $2 37 37 37 37] 37 1 s I I 1 t 3 3'7 g a4 37 29 3o 37 29 4-! a 27 25 36 34 E 24 !5 LLVLI own 26 1 f I4 I3 Patented May 30, 1972 3 Sheets-Sheet 1 ATTORNEY Patented May 30, 1972 3 Sheets-Sheet 5 ATTORNEY GRIPPING JAWS FOR COLD READING MACHINE 1n fonning what are usually referred to as button heads on tendons for prestressing concrete by the post tensioning method, the heads are formed, on high tensile strength steel wires, by a cold heading process. This may either be done at the plant at which the tendons are fabricated or at the place of use. When such cold heading is done at the place of use of the tendons, the high tensile strength steel wires usually are headed at one end thereof at the place of manufacture and are headed at the place of use at theother end thereof, in order to enable the insertion of the wires in a sheath which has been embedded in the concrete. In this method of post tensioning, the tendons are sent to the place of use with one end thereof unheaded and are pulled through the sheathing. In order to aid in the pulling of the wires through the sheathing and the tensioning thereof after the concrete has set, ,a greasy coating is applied to the wires which is both a lubricating means and a rust preventing means. While the gripping jaws for the wire in the heading machine are moved to and held in gripping engagement with the wire by means of a hydraulic cylinder, the force exerted perpendicularly to the force exerted by the hydraulic means operating the gripping jaws, which is used for cold heading the wire, is also produced by means of a hydraulic cylinder and is sufficient that, if the wire is greasy, difficulty is encountered in holding the wire from movement lengthwise of itself under pressure of the heading means because of the greasy character of the wire.

The heading machine used for cold heading the wire is of similar character to the machine for cold heading wire shown and described in the patent to Dabney et al., U.S. Pat. No. 3,333,456, Aug. 1, 1967. It has been found to be highly desirable, in order to firmly hold a greasy wire, to not only provide for gripping the wire at a plurality of spaced points along the length thereof, but to temporarily flex the wire out of straight line position so that it is undulating when gripped by the gripping jaws. This makes it possible to hold the high tensile strength steel wire to be headed so that it will not slip relative to the gripping jaws when the heading operation takes place.

It is accordingly the purpose of my invention to provide an improvement in a heading machine of the character shown and described in the patent to Dabney et al., above referred to, by providing a pair of gripping jaws that are relatively movable to grip a wire therebetween, each of the jaws having a plurality of wire engaging portions spaced longitudinally of the wire that is to be gripped thereby, the longitudinally adjacent wire engaging portions having wire receiving grooves and being offset so as to alternately grip the wire at positions that are minutely offset from each other transversely of the wire to deflect the gripped wire alternately in opposite directions, the deflection being so small that it will only be temporary, while the wire is being gripped, and thus less than sufficient to permanently deform the wire. In order to maintain the high tensile strength of the wire, so that it will operate satisfactorily for prestressing the concrete, in which it is mounted, such permanent deformation is undesirable, as even if small, it will have an undesirable weakening effect, where this takes place.

Preferably the machine, for cold heading the high tensile strength steel wire, is provided with a gripping jaw for the wire, which is mounted in fixed position in the machine, and a cooperating gripping jaw which is movable toward and away from the fixed jaw, into and out of wire gripping position, the jaws each being provided with projecting gripping portions that are spaced from each other lengthwise of the wire, that is being gripped, and with the gripping portions of the movable gripping jaw opposite the gripping portions of the fixed gripping jaw. The adjacent gripping portions on each of the jaws vary minutely in projection toward the other jaw, to provide what can be referred to as a longer wire gripping portion and a shorter wire gripping portion, arranged alternately along the gripping jaw, with the longer wire gripping portions of the movable gripping jaw being opposite the shorter wire gripping portions of the stationary jaw, and vice versa, .the difference in projection of the longer and shorter gripping portions being the same in both the fixed gripping jaw and the movable gripping jaw, so that the gripping portions of the movable and fixed gripping jaws are complemental to each other.

My improved machine for cold heading high tensile strength wire thus carries out a method of cold heading, which includes the gripping of the wire, adjacent an end thereof that is to be headed, at a plurality ofspaced points lengthwise thereof, to produce temporary undulations in the gripped portion of the wire, and cold heading the wire so gripped by a force applied to the wire endwise thereof, the temporary undulations being produced by minutely deflecting the wire alternately transversely of its length in opposite directions by the adjacent gripping means, the wire springing back into its normal straight position after being released by the gripping jaws.

Other objects and advantages of my invention will appear as the description of the drawings proceeds. I desire to have it understood, however, that I do not intend to limit myself to the particular details shown or described, except as defined in the claims.

In the drawings:

FIG. 1 is a plan view of the gripping jaws, and associated parts of a machine for cold heading high tensile strength steel wire, embodying my invention, the gripping jaws being in an open position.

FIG. 2 is a plan view of the gripping jaws showing fragmentary portions of the headingmachine adjacent thereto, the jaws being closed, or in work-gripping position.

FIG. 3 is a face view in elevation of the movable gripping FIG. 4 is a fragmentary vertical section on an enlarged scale through the gripping jaws, taken substantially on the broken line 4-4 of FIG. 2, and

FIG. 5 is a fragmentary view partly in section and partly in elevation, on a greatly enlarged scale.

Referring in detail to the drawings, my improved gripping jaws may be applied to a cold heading machine such as shown in the patent to Dabney et al., U.S. Pat. No. 3,333,456 on Machine for Cold Heading Wire, patented Oct. 1, l967. said machine is provided with a frame member 11 and a pair of horizontally extending bars 12 and 13 which are secured to the frame member 11 by suitable fastening elements 14; Mounted on the frame member 11 is a hydraulic cylinder 15 which has the head 16, and mounted on the bar 12 is a hydraulic cylinder 17 having the head 18. Extending from the hydraulic cylinder 17 is a piston rod'l9 which is provided with an enlargement 20 on which a movable clamping jaw body 21 is mounted. Secured to the clamping jaw body 21, by suitable fastening elements 22, is a gripping jaw 23. Mounted in fixed position on the bar 13 is a stationary clamping jaw body portion 24. Mounted on said gripping jaw body portion 24 is a stationary gripping jaw 25, which is secured to the clamping jaw body portion 24 by the fastening elements 26. The hydraulic cylinder 15 has a piston rod extending therefrom which is provided with a head 27 on which a heading die 28 is mounted.

The hydraulic cylinder 17 is provided with suitable controlling means for the supply of hydraulic fluid thereto, such as shown and described in the patent to Dabney et al., above referred to, so that the movable gripping jaw will be moved toward the stationary gripping jaw and held in work gripping position as the'heading operation takes place. The hydraulic cylinder 15 is provided with suitable controlling means for operating the heading die so as to move toward the gripping jaws to head the wire mounted in the gripping jaws after the gripping jaws have been moved into and are held in closed position, the controlling means and details of construction of the heading means being shown and described in said Dabney et a1. U.S. Pat. No. 3,333,456.

The gripping jaw 23 is provided with a plurality of projecting gripping portions 29 and 30, said projecting gripping portions alternating along the face of the gripping jaw 23 in the direction of length of the wire that is to be gripped thereby. The gripping jaw 23 is held in fixed position relative to the body portion 21 by means of a key 31 mounted in grooves 32 and 33 in the body portion 21 and in the gripping jaw 23, to assure the proper alignment of the said gripping jaw, with respect to the stationary gripping jaw, to be described more in detail below, and to take up the force exerted against the end of the movable gripping jaw by the heading die when the heading operation thereof is taking place. The stationary gripping jaw is provided with projecting gripping portions and 29, the gripping portions 30 of the jaw 25 being opposite the gripping portions 29 of the gripping jaw 23 and the gripping portions 29 of the gripping jaw 25 being opposite the gripping portions 30 of the gripping jaw 25. The gripping portions 29 of the two jaws 23 and 25 are of the same projection or length in both the gripping jaws 23 and 25, and the gripping portions 30 of both the gripping jaws 23 and 25 are of the same length or projection toward the other jaw. The gripping portions 29 are of greater length or projection toward the opposed gripping jaw than the gripping portions 30, the difference in projection of the gripping portions 29 and 30 being extremely small or minute. The stationary gripping jaw 25 is also held in fixed position relative to the body portion 24, and thus in alignment with the gripping jaw 23, by a key 34 which is mounted in grooves 35 and 36 in the body portion 24 and the gripping jaw 25, said key 34 taking up the force exerted against the end of the stationary gripping jaw 25 by the heading die.

The projecting gripping portions 29 and 30 are uniformly spaced so as to provide the grooves 37 between the same. Each of said gripping portions has a wire receiving groove 38. The grooves 38 are concavely curved to closely fit the contour of the wire to be gripped by the gripping jaws, the wire being shown at 39 in FIGS. 1 to 4, and 5. The grooves 38 are slightly less than semicylindrical so'that when the gripping jaws are in closed position, as shown in FIGS. 3,4 and 5, the forward edges of the projected gripping portions 29 and 30 are slightly spaced so as to provide the space 40 between the same. The heading die 28 is provided with a recess 41 receiving the end of the wire 39, comprising means for forming a portion of the button head, and the gripping jaws 23 and 24 have recesses 42 in the end walls thereof facing the heading mechanism, serving as forming die portions to complete the means for forming the head 43 on the wire.

As above pointed out, the gripping portions 29 project further toward the gripping portion of the opposite gripping jaw than the gripping portions 30. The difference in the projection of the portions 29 and 30 is very small. In the case of a one-fourth inch wire the difference in projection of these projecting portions is preferably 0.005 inch. Because of the difference in the projection of the gripping portions and the alternate arrangement thereof above described, the action of the adjacent gripping portions will be to cause a slight deflection of the wire in opposite directions which is so small that there is no permanent bending of the wire, the wire springing back into straight position when released from the gripping aws.

The action of the gripping jaws is illustrated in FIG. 5 in which the wire and the projected gripping portions 29 and 30 are enlarged, the difference between the gripping portions 29 and 30 being somewhat exaggerated. The gripping jaws 29 and 30 at the left of FIG. 5 will cause a deflection upward of the wire 39, while the action of the gripping jaws 29 and 30, shown at substantially the middle of FIG. 5 will deflect the wire 39 downwardly slightly, resulting in the temporary bend 44 in the portion of the wire 39 in the groove 37, due to 'the difference in the closed position of the paired gripping jaw portions 29 and 30 at the right of said groove 37, and at the left thereof. At the right of FIG. 5 the gripping portions 29 and 30 again deflect the wire 39 upwardly which results in a bend 45 in the opposite direction to the bend 44 in the groove 37, shown to the right of the center of FIG. 5. This slight bending in opposite directions of the wire 39 results in the wire having an undulating character at the gripped portion thereof. This deflection of the wire out of straight line position is, however, so small that it does not in any way affect the tensile strength of the wire, and only temporarily deflects the wire, the wire strai htening out when it is released by the gripfiing jaws. As a resu t the wire IS much more firmly gripped t an if a single movable gripping jaw and a single stationary gripping jaw were provided, as in the Dabney et al. patent, and the resistance to any longitudinal movement of the wire 39, due to the force exerted thereon on the end thereof by the heading die 28, is such that there is no movement of the wire under the action of the die relative to the gripping means lengthwise of the wire 39. While the gripping action of the gripping jaws is greatly increased by this arrangement of projecting gripping portions on any wire gripped by said jaws, it is particularly important in preventing any relative movement of a greased wire relative to the gripping jaws, when the heading operation is taking place. The actual difference in projection of the shorter and longer gripping portions may be increased as the diameter of the wire gripped increases, the increase in the difference of projection of the alternating projecting gripping portions being kept small enough that the wire gripped by the gripping jaws will not be permanently bent.

I claim:

1. A machine for cold heading high tensile strength wire having a pair of gripping jaws relatively movable to grip a wire therebetween, each of said jaws having wire gripping portions projecting therefrom, said gripping portions being spaced longitudinally of the gripped wire, the gripping portions of one of said jaws being opposite the gripping portions of the other jaw, the wire gripping portions of each of said jaws alternating minutely in projection toward the other jaw to provide alternating minutely longer and shorter gripping portions on each of said jaws, the longer gripping portions of said jaws all having the same projection and the shorter gripping portions of said jaws all having the same projection and the longer gripping portions of each jaw cooperating with the shorter gripping portions of the other jaw to have wire gripping positions for longitudinally adjacent cooperating gripping portions that are minutely ofiset transversely of said wire to minutely deflect a gripped high tensile strength wire in opposite directions to produce undulations in said wire less than suffi-' cient to permanently deform said wire.

2. The machine for cold heading high tensile strength wire claimed in claim 1 in which wire engaging grooves closely fitting the gripped wire are provided in said projecting gripping portions of said jaws spaced lengthwise of the gripped wire, said grooves being slightly less than semi-cylindrical.

3. The machine for cold heading high tensile strength wire claimed in claim 1 in which one of said jaws is mounted in fixed position and the other jaw is movable toward and away from said one jaw into and out of wire gripping position. 

1. A machine for cold heading high tensile strength wire having a pair of gripping jaws relatively movable to grip a wire therebetween, each of said jaws having wire gripping portions projecting therefrom, said gripping portions being spaced longitudinally of the gripped wire, the gripping portions of one of said jaws being opposite the gripping portions of the other jaw, the wire gripping portions of each of said jaws alternating minutely in projection toward the other jaw to provide alternating minutely longer and shorter gripping portions on each of said jaws, the longer gripping portions of said jaws all having the same projection and the shorter gripping portions of said jaws all having the same projection and the longer gripping portions of each jaw cooperating with the shorter gripping portions of the other jaw to have wire gripping positions for longitudinally adjacent cooperating gripping portions that are minutely offset transversely of said wire to minutely deflect a gripped high tensile strength wire in opposite directions to produce undulations in said wire less than sufficient to permanently deform said wire.
 2. The machine for cold heading high tensile strength wire claimed in claim 1 in which wire engaging grooves closely fitting the gripped wire are provided in said projecting gripping portions of said jaws spaced lengthwise of the gripped wire, said grooves being slightly less than semi-cylindrical.
 3. The machine for cold heading high tensile strength wire claimed in claim 1 in which one of said jaws is mounted in fixed position and the other jaw is movable toward and away from said one jaw into and out of wire gripping position. 